
In fact it is described as beneath:

Ordinary flame retarded cables – These cables when exposed to fire emit corrosive gases and combustion.
Low halogen fire retardant cables – These emit low halogen acid gas and less corrosive and smoke after combustion
Low smoke zero halogen fire retardant cables – These are even better emitting no halogen acid gas, less corrosive gas and very less fuming. It possesses excellent fire retardant property. These are widely used in nuclear power plants, subway stations, telephone switching and computer control centers, high-rise buildings, hotels, radio and television stations, important military facilities, oil platforms, etc. Both the above categories maintain the mechanical, electrical and physical properties to meet operating requirements of the cable.
Oxygen Barrier Cable – These are also known as highly flame retardant cables. A layer of non-softening, non-combustible, halogen-free, smoke-free, heatproof plastic material is filled or wrapped between the cable protected center and the cable sheath, i.e. insulating natural is utilized to confine the cable from the outside oxygen gas, with the goal that the cable is non-flammable or flame retardant. It is advisable to prefer the last three depending upon their cost as the burning of ordinary fire retardant cables may lead to emission of hazardous gaslike chlorine gas that is poisonous and is dangerous for human beings. This forms hydrochloric acid if comes in contact with water can further deteriorate the problem as it can have a destructible effect on the adjacent equipment. Zero halogen and oxygen barrier cables have better fire retardant properties, low toxic and corrosive gas emissions, and low smoke emission.